Understanding MRSA, and How to Avoid Contracting It.

MRSA — short for methicillin resistant Staphylococcus aureus — is a bacteria that can cause nasty pus-filled skin abscesses. Even worse, it sometimes invades the body to cause serious infections in the joints, bloodstream, lungs or other tissues.

Methicillin is an antibiotic first used in 1959 to treat Staph infections resistant to penicillin. Of course, bacteria soon evolved to become resistant to methicillin, and the first case of MRSA was reported in 1961 in a hospitalized patient. At first, hospital acquired MRSA (HA-MRSA) infections were rare, accounting for only 2 percent of hospital Staph infections in 1974. But over time this increased to 22 percent in 1995, and 50 percent in 1997.

But MRSA hasn’t remained confined to hospitals. Community acquired MRSA (CA-MRSA) was first identified in 1981. And now it is common, although the incidence seems to be dropping. The last year for which I could find statistics, 2013, we had over 16,000 cases of invasive MRSA in the US. But clearly there are many more cases involving the skin. Scarcely a day passes in the urgent care where there is not at least one patient with a MRSA skin or soft tissue infection.

People often wonder where their infection came from. Unless you are a hermit without other human contact, you are likely to touch something in your daily life that has been touched by another human colonized with MRSA — a door knob, a shopping cart, gym equipment, etc. The colonized person often has no infection because the bacteria is living peacefully on their skin or in their nose. Yes, MRSA loves to live in the nose, and we humans often unwittingly transfer bacteria from our noses to our hands to an inanimate object or directly to someone else’s hand. Then the process goes in reverse — from inanimate object, to hand, to nose. And so another person is colonized.

Most colonized people aren’t sick and have no symptoms from their MRSA. Whether someone becomes ill depends on three factors: virulence, numbers, and resistance.

Think of virulence as nastiness, whether a MRSA strain is a vicious pit bull or docile pussy cat. Numbers matter because a big gang of germs is more dangerous than a single bug. And people vary in their ability to resist infection due to factors such a innate genetic resistance, nutrition, current medications, and underlying medical illnesses.

Believe it or not, much MRSA transmission occurs between household members. Fortunately there are ways to reduce the spread of MRSA.

First, keep any MRSA wounds covered. Leaving them open won’t cause a wound to dry up and heal faster, but will give the bacteria free rein to wander onto other people. And don’t share personal items. Wash laundry, towels, and sheets in hot water to kill MRSA bacteria.

There are some other things to try that aren’t proven, but are safe and probably worth a shot. First, clean commonly touched surfaces once or twice a day. This includes doorknobs, the TV remote, appliance handles, etc. Use a product active against S. aureus, such as bleach-containing sprays or wipes, or a disinfectant such as Lysol. Although, alas, resistance to the active ingredient in Lysol, bezalkonium chloride, has been reported.

Sometimes the prescription antibiotic ointment mupirocin, placed in each nostril twice a day for 5 days, can help reduce nasal MRSA numbers. Bathing with the over-the-counter disinfectant chlorhexidine (Hibiclens is one brand) for 5-14 days may reduce skin colonization. Or bleach baths are sometimes used — 1/4 cup of bleach in a 1/4-filled bath tub for 15 minutes, twice a week, for three months.

If despite these measures you develop symptoms of an abscess, don’t wait to see if it will go away. Often things get worse fast and become more difficult to treat. So seek medical care promptly.

Eva Briggs is a medical doctor who works at two urgent care centers (Central Square and Fulton) operated by Oswego Health.